ICLS6022J Datasheet, PDF (23/33 Pages) Infineon Technologies AG – LED System Driver ICs

LED System Driver ICs
ICLS6x Series
Functional Description
The other fault detection function which can result in the Auto Restart mode during startup and has the 8.0 µs
blanking time is for overtemperature detection. This block checks for a junction temperature of higher than 140 °C
for malfunctioning operation.
Once Auto Restart mode is entered, the internal bias is switched off in order to reduce the current consumption of
the IC as much as possible. In this mode, the average current consumption is only 300 µA as the only working
blocks are the reference block and the Undervoltage Lockout (UVLO), which controls the startup cell by switching
on/off at V_VCCon/V_VCCoff.
As there is no longer a self supply provided by the auxiliary winding, VCC starts to drop. The UVLO switches on
the integrated startup cell when VCC falls below 10.3 V. It continues to charge VCC up to 18 V, at which point it
is switched off again and the IC enters the startup phase.
Once all fault conditions have been removed, the IC automatically powers up as usual with a switching cycle at
the GATE output after the soft start period has elapsed – hence the name Auto Restart mode.
3.6.2.2 Auto Restart Mode during RUN Mode
In the case of overload or open loop, the FB voltage exceeds 4.5 V, which is observed by C4. At this time, the
external soft start capacitor can then be further charged by the integrated pull-up resistor R_SoftS via the switch S3
(see Figure 15). If V_SoftS exceeds 4.0 V, which is observed by C3, Auto Restart mode during RUN mode is
activated as both inputs of the gate G5 are high.
SoftS
C3
4.0V
4.5V
C4
FB
Internal
Bias
Auto
&
Restart
Mode
G5
Control Unit
Figure 17 Auto Restart mode during RUN mode
This charging of the soft start capacitor from 3.2 V ~ 3.6 V to 4.0 V defines a blanking window, which prevents the
system from entering Auto Restart mode during RUN mode unintentionally during large load jumps. In this event,
FB will rise close to 5.0 V for a short duration before the loop regulates FB to less than 4.5 V.
In the case of VCC undervoltage – i.e., VCC falls below 10.3 V, the IC is turned off with the startup cell charging
VCC as described earlier in this section. Once VCC is charged to above 18 V, the IC starts a new startup cycle.
This blanking time window for the Floating Load Protection mode can be forced via the external C_SoftS capacitor.
3.6.2.3 Floating Load Protection (FLP)
The circuit starts up as usual, but a missing load leads to a rise in the output and auxiliary voltages.
Reaching the VCC threshold of 24.5 V (voltage divider RD2/R4 and Q2) leads to a reduction in the feedback
voltage and hence to reduced output current pulses in order to keep the output voltage below the maximum rating
of the components. If the feedback level falls below 1.35 V, the Soft Start voltage begins to rise up to a threshold
of 4 V (depends on the C4 value) and the IC is switched into the FLP mode.
Data Sheet
23
Version 1.0, 2011-05-19